The science of decay and decomposition

The Corpse Project wants the public to have much clearer information about the dead body, the science and value of decomposition and how the natural cycle works, so we can make better choices. It is pulling together research –  environmental, social and cultural –  that can help us.

How dead bodies affect the soil – the criminal interest

Much research on how animal decomposition affects the soil takes place to help with analysing crime or archaeological scenes. Moisture, temperature and the nature of the soil are key factors in the rate of decay and, if these are understood and taken into account, the forensic scientist can work out how long the body has been there. Soil bacteria and chemical changes are also of interest to the forensic world – what they are and how long they have been there – because these changes can also suggest how long remains have been in place, influencing the microbial and chemical composition of the soil.

How dead bodies can help the soil – the natural cycle

We are looking at this from another perspective – ie the input that the body can make to the soil. There has been less research interest in this, but existing forensic research can help us. It is known for example that one year after a pig carcass (often used in research instead of a human body) has been put on the soil surface, significant increases in nitrogen and phosphate can been found in the soil underneath, but not after three years. Nitrogen and phosphate are of course common components of garden fertiliser. The body is not a ‘waste product’.

Plant growth is suppressed for one year as the body decomposes but there is lush growth three years after the carcass was placed on the soil. This suggests that there is a peak time for soil conditioning from remains and when it might benefit plant growth. How might this be made best use of if we wanted human remains to contribute to the natural cycle? Would we consider exhuming bones so that the soil could be reconditioned on a cyclical basis, or would this be culturally unacceptable?

Anderson B, Meyer J, Carter DO, Dynamics of ninhydrin-reactive nitrogen and pH in gravesoil during the extended postmortem interval, Journal of Forensic Science 2013 Sept 58(5)

Greek grandmothers

Touching briefly on the social sciences, a very moving book, The Death Rituals of Rural Greece, by Loring M Danforth with photography by Alexander Tsiaras (Princeton University Press 1982), is a study of the practice of exhuming the bones of loved ones in an area with more rocks than soil and therefore little option of permanent burial of the whole body. It documents the ritual mourning, led by women with songs of lamentation and the cleaning of the bones, continued some years after the person has died. Could we in the UK find new ways to mediate between life and death and in the process make more efficient use of the land and soil?

The Tennessee body farm and soil fertility

Returning to soil changes with the dead body, The University of Tennessee Anthropology Research Facility (ARF) is famous as a facility for study of the decomposition of human remains, with human corpses laid outside in different settings  and their changes recorded. Again, this has a forensic focus, but a study of the soil, with its long-term history of continuous decomposition, has found it to be fairly uniformly enriched by high-quality nutrients, compared with the soil outside the facility. This raises the question of whether generalised fertilising of a site which was also used for grass or grazing could be achieved by simple, shallow burial at the right density.

Damann FE, Tanittaisong A, Carter DO, Potential carcass enrichment of the University of Tennessee Anthropology Research Facility: a baseline study of edaphic features. Forensic Science International,2012 October.

Animal remains and the natural cycle

The benefits of cadavres to the soil are multiple and they support other creatures and the whole ecosystem. As much as 5,000kg of cadaver can be introduced to a square kilometre a year (where there are US bison!) ‘Cadaveric materials are rapidly introduced to below ground floral and faunal communities, which results in the formation of a highly concentrated island of fertility, or cadaver decomposition island (CDI). CDIs are associated with increased soil microbial biomass, microbial activity… and nematode abundance’. CDIs release energy and nutrients into the wider ecosystem and receive materials such as dead insects and faecal matter and feathers from scavengers. CDIs are a specialised habitat for a number of flies, beetles and pioneer vegetation, which increases biodiversity. Increased soil carbon, nutrients and pH is present in a CDI during advanced decay. Bison can affect the structure of plant communities for at least five years.

Carter D.O, Yellowlees D, Tibbett M, Cadaver decomposition in terrestrial ecosystems, Naturwissenshaften, 2007, 94.

What if the body is shallow buried and not on the surface?

It seems that there is significant environmental value in the decay of cadavres on the surface. However, this is clearly not an option for human corpses. If these were buried in shallow graves would they still provide such benefits? How shallow would they need to be? There has been scant research into the effects on the soil of the shallow burial of human remains and whether they can decompose rapidly.

In an experiment with rabbits buried at 35cm depth, those which had been exposed to insects before burial decomposed 30% more quickly than those which had not. The role of insects is critical in the decomposition process and indeed, the funeral director wants to stop body orifices allowing blowflies from depositing eggs and thus triggering decomposition. Do they still have an effect once a body is buried? This experiment with rabbits suggests that they can and that allowing flies access to a body and then burying it in a shallow grave would result in relatively rapid decomposition in the right conditions. 

Bachmann J, Simmons T, 2010, The influence of preburial insect access on the decomposition rate . Forensic Science International 2010 July 55(4)

What if burial is not the best option?

Tower Hamlets borough, in London, has just bought land in Kent as a burial site for its residents, because there is no land left in the borough. Is this a sustainable option, with the travel and expense of using land outside London in the hothouse of the South East? The Corpse Project will look at the value of cremation and good use of ‘ashes’ as an alternative to burial.

Our look at the science so far makes us ask some interesting questions:

Could bodies buried shallow decompose quickly in the right conditions and contribute to the natural cycle?

What density of bodies could help enrich a whole field?

Are there other good ways of returning the dead body to the natural cycle?

What do we feel about the reuse of sites and the exhumation of remains?

Do human remains (‘ashes’) after cremation have value for the natural cycle and how should we use them?

Is woodland burial a good sustainable option?

And through all of this is the human dimension – what kinds of rituals and remembrances do we need?

”Three flies could consume a horse cadaver as rapidly as a lion”. Linnaeus, 1767.